A photographic apparatus has heretofore been developed for obtaining a record of the internal condition of a pipeline and it has been found to be highly advantageous, especially in connection with the testing of offshore pipelines used for transporting natural gas in its raw state. Natural gas cannot be safely treated offshore and may produce corrosion when transported in its raw state through steel pipe of a pipeline, especially when the temperature is relatively high as is often the case. Natural gas in its raw state may include a combination of carbon dioxide and free water which is operative to produce carbonic acid and which will corrode steel. The effect can be augmented by an erosion effect when the rate of flow is high and at bends and over weld beads or the like where the flow is turbulent.
The effect of such corrosion and erosion as well as other defects can eventually lead to complete failure of the pipe. If such defects can be detected at an early time, it is possible to repair the pipe or otherwise take corrective measures. For example, it is possible to move devices known as "pigs" through a pipe and by moving a series of such pigs through a pipe it can be cleaned, etched, washed, dehydrated and then coated with a protective coating such as an epoxy.
In the apparatus heretofore developed, an image is projected through a film plane from an internal surface area of the pipe along a viewing axis which is normal to the axis of the pipe, a generally rectangular image being used in the film plane which corresponds to a generally rectangular internal surface area of the pipe. With this arrangement, it is possible to obtain a photographic record which can be accurately interpreted and which indicates when repair or maintenance procedures are necessary. Preferably, the camera and associated optical means and illumination means are located within a chamber between forward and rearward cup assemblies in a device which is movable through the pipeline by the pressure of fluid within the pipeline.
Another feature of the apparatus as heretofore developed is in the provision of weight means such that the orientation of the viewing axis may be fixed relative to a vertical position. Normally, it is desirable to place the viewing axis at a "six o'clock" position because it is found that the areas of primary interest are those in the lower side of the pipe where water might accumulate and lead to corrosion and/or erosion of the pipe.